Currently, an exhaust gas purification apparatus in which a diesel particulate filter (DPF) is used is practically used as an apparatus that collects fine particles such as particulate matter (PM) contained in the exhaust gas. Since, in such an exhaust gas purification apparatus, fine particles such as PM are deposited on the DPF through use thereof, regeneration of the DPF is demanded. As a method for regenerating the DPF, for example, a method is disclosed in which a high-frequency electromagnetic wave such as a microwave irradiated from a microwave irradiation apparatus is used. In particular, according to the method, regeneration of the DPF is performed by irradiating an electromagnetic wave such as a microwave on the DPF to heat and combust fine particles such as PM deposited on the DPF.
A microwave irradiation apparatus is used also in a food heating apparatus for heating food, a chemical reaction apparatus or the like.
In the exhaust gas purification apparatus described above, regeneration of a DPF is performed by irradiating an electromagnetic wave such as a microwave on the DPF to dielectrically heat fine particles such as PM to oxidize and decompress the fine particles such as PM. However, it is difficult to irradiate a microwave, which is to be irradiated on the DPF, with a uniform intensity in the DPF, and a high intensity region and a low intensity region of the microwave appear in the DPF, resulting in unevenness of the temperature in the DPF. Therefore, fine particles such as PM are removed in some region while fine particles are not removed very much in another region in the DPF, and the DPF is not regenerated sufficiently. The phenomenon that a region which the intensity of an irradiated microwave is high and another region in which the intensity of the irradiated microwave is low appear in this manner similarly occurs also with a food heating apparatus, a chemical reaction apparatus and so forth.
Therefore, a microwave irradiation apparatus is demanded in which a region in which the intensity of an irradiated microwave is high and another region in which the intensity of the irradiated microwave is low are less likely to appear and a heating target may be heated uniformly.
The followings are a reference documents.
[Document 1] Japanese Laid-open Patent Publication No. 2006-140063
[Document 2] Japanese Laid-open Patent Publication No. 4-179817
[Document 3] Japanese Patent No. 4995351
[Document 4] Japanese Laid-open Patent Publication No. 05-202733
[Document 5] Japanese Laid-open Patent Publication No. 2014-175122